1. Field of the Invention
The present invention relates, in general, to a molten strand feeding device used for controllably feeding molten resin strands to a strand granulator while removing first bad strands during a thermoplastic forming process and, more particularly, to a strand feeding device not only provided with a strand cutting means, suitable for effectively removing the bad strands at the very beginning of the molten strand emerging from the nozzles, but also easily changed between the horizontal and vertical types.
2. Description of the Prior Art
In a process of forming fabrics or other products from molten thermoplastic resin, the molten thermoplastic resin is primarily formed into strands using extrusion nozzles of a nozzle surface prior to being fed to a strand granulator. The molten resin strands, emerging from the extrusion nozzles, are fed onto a cooling trough (hereinbelow, selectively called by the term "cooling trough", "discharge trough" or "drainage trough") thus being cooled prior to being fed to a strand granulator. As the molten resin strands emerge from the extrusion nozzles, the start strands typically have bad quality due to difference in heating temperatures or bad match of colors so that it is necessary to remove the bad strands at the very beginning of the strand emerging from the nozzles.
FIG. 7 shows a conventional horizontal-type strand feeding device disclosed in U.S. Pat. No. 4,528,157, while FIG. 8 shows a conventional vertical-type strand feeding device disclosed in Japanese Patent Publication No. 89-39323.
In the conventional horizontal-type device (disclosed in the above U.S. patent), a slidably movable segment is placed at the upper end of the cooling or discharge trough in a way such that it is movable between operating and non-operating positions as shown in FIG. 7. A separating element is installed at a position above the cooling trough and is operated in cooperation with the movable segment. The above separating element of the device cuts away the bad strands as the movable segment is in its operating position. Meanwhile, when the movable segment is in its non-operating position, the strands are permitted to freely pass down at the side of the cooling trough.
In the above device, the movable segment moves horizontally between the operating and no-operating positions, while the nozzle surface is inclinedly arranged relative to the horizontal moving passage of the movable segment at an angle of inclination. Due to the positional relation between the movable segment and the nozzle surface, the cutter integrated with the tip of the separating element primarily comes into pressurized contact with the nozzle surface prior to sliding on the inclined nozzle surface when it cuts away the bad strands emerging from the nozzles. In this regard, the cutter of the separating element may be bent, deformed or exceedingly abraded as it repeatedly comes into pressurized contact with the nozzle surface and cuts away the bad strands emerging from the nozzles. The cutter thus fails to be brought into close contact with or to smoothly move on the nozzle surface thereby reducing the operational effect while cutting away the bad strands.
Another problem of the horizontal-type device resides in that the discharge trough is fixedly arranged horizontally so that the position of the trough cannot be adjusted even when the inclination angle of the nozzle surface is unexpectedly changed into another angle.
Meanwhile, the vertical-type device (disclosed in the above Japanese patent) includes at least one nozzle and a drainage trough. The drainage trough controllably feeds the molten resin strand emerging from the nozzle. The drainage trough comprises an upper end, which selectively guides the strand to one of two passages: a strand feeding passage extending onto the trough and a strand falling passage extending at the side of the trough. The device also has a strand collector, which is arranged on the strand falling passage at the side of the trough and collects the strand falling down from the nozzle. The drainage trough is rotatable around a rotating shaft so that the trough can move between operating and non-operating positions. In its operating position, the trough is placed on the strand falling passage thus catching the strand emerging from the nozzle. When the trough is in its non-operating position, it is spaced apart from the strand falling passage, thus failing to catch the strand and permitting free passage of the strand at the side of the trough. In the operating position of the drainage trough, the upper end of the trough is brought into its operating position at which the upper end of the trough guides the strand onto the lower end of the trough. The upper end of the trough can be moved into its non-operating position permitting free passage of the strand at the side of the trough.
In the above vertical-type device, the upper end of the trough has to rotate around the rotating shaft relative to the horizontal nozzle surface so that it is brought into its strand cutting position. Such a rotating motion of the upper end reduces the strand cutting effect of the device.
Another problem of the vertical-type device resides in that the discharge trough is fixedly arranged vertically so that the position of the trough cannot be adjusted even when the angle of the nozzle surface is unexpectedly changed into another angle.